I've rarely taken along a spare (calculated risk) although I would like to buy a cheap aluminum/plastic one for prying in rocks (something I'd never do with my wooden one).  I'm extremely careful with my one and only wooden one- handmade by my dad, and with a painting on it as well, done by him.  NO ONE goes near my paddle but me!  (If you break it, I'd have to break you!) I realize accidents do happen, but I've been lucky so far (knock on wood- hope I didn't just jinx myself :)- will bring along spare next time just in case! :)